1. Field of the Invention
This invention relates to a photo detecting device. In addition, this invention relates to a distance measuring apparatus. Furthermore, this invention relates to a distance and image measuring apparatus.
2. Description of the Related Art
There is a conventional distance measuring apparatus mounted on a vehicle. The conventional apparatus intermittently emits a laser beam into a predetermined angular range outside the body of the vehicle. The predetermined angular range is scanned by the laser beam. Thus, the predetermined angular range is also referred to as the scanned range. When an object in the scanned range reflects the laser beam, a portion of the laser beam returns to the apparatus as an echo. The apparatus measures the time difference between the timing of the emission of the laser beam and the timing of the reception of the echo. The apparatus calculates the distance to the object on the basis of the measured time difference. The scanned range corresponds to a detection area. Basically, it is desirable to provide a wide scanned range, that is, a wide detection area.
When the scanned range is excessively wide, the following problems arise. The apparatus on the present vehicle receives a laser beam emitted from an apparatus on another vehicle running on the opposite lane. The received laser beam interferes with a distance measurement by the apparatus on the present vehicle. The apparatus on the present vehicle receives an echo related to an apparatus on another vehicle running on an adjacent lane. The received echo interferes with a distance measurement by the apparatus on the present vehicle.
U.S. Pat. No. 5,760,886 corresponding to Japanese published unexamined patent application 7-98381 discloses a scanning-type distance measurement device which is responsive to selected signals to reduce interference due to stray light. An emitted beam of light is aimed to be reflected from an object toward a photodetector among a plurality of photodetectors which are positioned linearly or in two dimensions. The outputs of the photodetectors are selected based on the position of the emitted beam of light to ignore photodetectors which should not contribute to the reflected beam. The approach in U.S. Pat. No. 5,760,886 reduces the effects of stray noise from other light sources. The selection of the photodetectors is synchronized with a scanning light emitter by a position signal and an angular signal so that the noise component in the output signal can be kept to a minimum.
In the device of U.S. Pat. No. 5,760,886, a switch is provided between a timing circuit and an array of photodetectors. The switch selects one from among the photodetectors, and transmits the output signal of the selected photodetector to the timing circuit. A possible problem in the device of U.S. Pat. No. 5,760,886 is as follows. The output signals of the non-selected photodetectors leak to the timing circuit through the switch. Therefore, in the case where a non-selected photodetector receives stray light, a noise signal leaks therefrom to the timing circuit. In this case, the timing circuit responds to the noise signal.
It is a first object of this invention to provide an improved photo detecting device.
It is a second object of this invention to provide an improved distance measuring apparatus.
It is a third object of this invention to provide an improved distance and image measuring apparatus.
A first aspect of this invention provides a photo detecting device comprising a processing circuit; an output line leading to the processing circuit; a ground line; an array of pixels including respective photo detecting zones for changing incident light into corresponding electric signals through photoelectric conversion, wherein each of the pixels includes a first switch for selectively connecting and disconnecting a related photo detecting zone to and from the output line, and a second switch for selectively connecting and disconnecting the related photo detecting zone to and from the ground line; means for causing the second switch to disconnect the related photo detecting zone from the ground line when the first switch connects the related photo detecting zone to the output line; and means for causing the second switch to connect the related photo detecting zone to the ground line when the first switch disconnects the related photo detecting zone from the output line.
A second aspect of this invention is based on the first aspect thereof, and provides a photo detecting device wherein the photo detecting zone of each of the pixels comprises a pin photodiode, and the first and second switches are formed in well layers separate from the photo detecting zone.
A third aspect of this invention is based on the first aspect thereof, and provides a photo detecting device further comprising a matrix arrangement of pixels provided in the array of pixels, common lines provided in the output line, wherein pixels in one of one-direction pixel groups in the matrix arrangement are connected to one of the common lines, a third switch for selectively connecting and disconnecting one of the common lines to and from the processing circuit, a fourth switch for selectively connecting and disconnecting one of the common lines to the ground line, means for causing the fourth switch to disconnect the related common line from the ground line when the third switch connects the related common line to the processing circuit, and means for causing the fourth switch to connect the related common line to the ground line when the third switch disconnects the related common line from the processing circuit.
A fourth aspect of this invention is based on the third aspect thereof, and provides a photo detecting device further comprising first control lines each for controlling the first switches in one of row-direction pixel groups in the matrix arrangement, second control lines each for controlling the second switches in one of the row-direction pixel groups in the matrix arrangement, a third control line for controlling the third switch, and a fourth control line for controlling the fourth switch.
A fifth aspect of this invention is based on the first aspect thereof, and provides a photo detecting device further comprising a capacitor provided in each of the pixels for storing electric charges generated by the related photo detecting zone in response to the incident light, an image-signal output line leading to the processing circuit, a fifth switch provided in each of the pixels for selectively connecting and disconnecting the photo detecting zone to and from the capacitor, a sixth switch for selectively connecting and disconnecting the capacitor to and from the image-signal output line, the second switch being for selectively connecting and disconnecting the capacitor to and from the ground line, and means for causing the second switch to connect the capacitor to the ground line during a predetermined time interval after causing the sixth switch to connect the capacitor to the image-signal output line.
A sixth aspect of this invention is based on the fifth aspect thereof, and provides a photo detecting device further comprising a matrix arrangement of pixels provided in the array of pixels, common image-signal lines provided in the image-signal output line, wherein pixels in one of one-direction pixel groups in the matrix arrangement are connected to one of the common image-signal lines, and a seventh switch for selectively connecting and disconnecting one of the common image-signal lines to and from the processing circuit.
A seventh aspect of this invention provides a photo detecting device comprising a processing circuit; a matrix arrangement of pixels including respective photo detecting zones for changing incident light into corresponding electric signals through photoelectric conversion; common output lines leading to the processing circuit and each provided for pixels in one of one-direction pixel groups in the matrix arrangement; a ground line; a first switch provided in each of the pixels for selectively connecting and disconnecting a related photo detecting zone to and from one of the common output lines; a third switch for selectively connecting and disconnecting one of the common output lines to and from the processing circuit; a fourth switch for selectively connecting and disconnecting one of the common output lines to and from the ground line; means for causing the fourth switch to disconnect the related common output line from the ground line when the first switch connects the related photo detecting zone to the common output line and the third switch connects the related common output line to the processing circuit; and means for causing the fourth switch to connect the related common output line to the ground line when the first switch disconnects the related photo detecting zone from the common output line and the third switch disconnects the related common output line from the processing circuit.
An eighth aspect of this invention provides a photo detecting device comprising a processing circuit; a matrix arrangement of pixels including respective photo detecting zones for changing incident light into corresponding electric signals through photoelectric conversion; a last-stage output line leading to the processing circuit; common output lines connected to the last-stage output line and each provided for pixels in one of one-direction pixel groups in the matrix arrangement; a ground line; a first switch provided in each of the pixels for selectively connecting and disconnecting a related photo detecting zone to and from one of the common output lines; a third switch for selectively connecting and disconnecting one of the common output lines to and from the last-stage output line; a fourth switch for selectively connecting and disconnecting the last-stage output line to and from the ground line; means for causing the fourth switch to disconnect the last-stage output line from the ground line when the first switch connects the related photo detecting zone to the common output line and the third switch connects the related common output line to the last-stage output line; and means for causing the fourth switch to connect the last-stage output line to the ground line when the first switch disconnects the related photo detecting zone from the common output line and the third switch disconnects the related common output line from the last-stage output line.
A ninth aspect of this invention is based on the seventh aspect thereof, and provides a photo detecting device further comprising means for causing the first switch to connect the related photo detecting zone to the common output line and causing the third switch to connect the related common output line to the processing circuit when the fourth switch connects the related common output line to the ground line, and then causing the fourth switch to disconnect the related common output line from the ground line.
A tenth aspect of this invention is based on the seventh aspect thereof, and provides a photo detecting device further comprising a capacitor provided in each of the pixels for storing electric charges generated by the related photo detecting zone in response to the incident light, an image-signal output line leading to the processing circuit, a fifth switch provided in each of the pixels for selectively connecting and disconnecting the photo detecting zone to and from the capacitor, a sixth switch for selectively connecting and disconnecting the capacitor to and from the image-signal output line, a seventh switch for selectively connecting and disconnecting the image-signal output line to and from the processing circuit, and an eighth switch for selectively connecting and disconnecting the image-signal output line to and from the ground line.
An eleventh aspect of this invention is based on the fifth aspect thereof, and provides a photo detecting device further comprising means for connecting the photo detecting zone and the capacitor in series in each of the pixels, and an amplifier circuit provided between the sixth switch and the image-signal output line.
A twelfth aspect of this invention is based on the fifth aspect thereof, and provides a photo detecting device further comprising means for connecting the photo detecting zone and the capacitor in parallel in each of the pixels, means for precharging the capacitor, means for discharging the capacitor in response to the incident light applied to the photo detecting zone, and means for causing the first switch to connect the photo detecting zone to the output line to output the electric signal to the output line, and then causing the sixth switch to connect the capacitor to the image-signal output line to output the electric charges to the image-signal output line.
A thirteenth aspect of this invention is based on the fifth aspect thereof, and provides a photo detecting device further comprising fifth control lines each for controlling the fifth switches in one of row-direction pixel groups in the matrix arrangement, and sixth control lines each for controlling the sixth switches in one of the row-direction pixel groups in the matrix arrangement.
A fourteenth aspect of this invention provides a distance measuring apparatus comprising light applying means for applying laser light; a photo detecting device for detecting reflected light caused by reflection of the laser light applied by the light applying means at an object, the photo detecting device including a plurality of pixels; changing and selecting means for changing and selecting a pixel among the pixels in the photo detecting device as an active pixel; time difference measuring means for measuring a time difference between a moment of application of the laser light by the light applying means and a moment of detection of the reflected light by the photo detecting device; and distance calculating means for calculating a physical quantity representative of a distance to the object on the basis of the time difference measured by the time difference measuring means; wherein the photo detecting device comprises a photo detecting device of the first aspect of this invention.
A fifteenth aspect of this invention is based on the fourteenth aspect thereof, and provides a distance measuring apparatus wherein the changing and selecting means comprises means for changing and selecting a pixel among the pixels in the photo detecting device as an active pixel in response to a direction of application of the laser light.
A sixteenth aspect of this invention is based on the fourteenth aspect thereof, and provides a distance measuring apparatus which is mounted on a vehicle, wherein a direction of travel of the laser light corresponds to one of a vehicle width-wise direction and a vehicle height direction with respect to the vehicle.
A seventeenth aspect of this invention provides a distance and image measuring apparatus comprising light applying means for applying laser light; a photo detecting device for detecting reflected light caused by reflection of the laser light applied by the light applying means at an object, and for generating an image signal in response to the detected reflected light; time difference measuring means for measuring a time difference between a moment of application of the laser light by the light applying means and a moment of detection of the reflected light by the photo detecting device; distance calculating means for calculating a physical quantity representative of a distance to the object on the basis of the time difference measured by the time difference measuring means; and image measuring means for measuring an image on the basis of the image signal generated by the photo detecting device; wherein the photo detecting device comprises a photo detecting device of the fifth aspect of this invention.
An eighteenth aspect of this invention is based on the seventeenth aspect thereof, and provides a distance and image measuring apparatus further comprising means for changing an intensity of the laser light applied by the light applying means in accordance with the image measured by the image measuring means.
A nineteenth aspect of this invention provides a photo detecting device comprising a photodiode; a signal output line; a ground line; a first switch provided between the photodiode and the signal output line for selectively connecting and disconnecting the photodiode to and from the signal output line; and a second switch provided between the ground line and a junction between the photodiode and the first switch for selectively connecting and disconnecting the ground line to and from the junction between the photodiode and the first switch.
A twentieth aspect of this invention is based on the nineteenth aspect thereof, and provides a photo detecting device further comprising a last-stage signal transmission line; a third switch provided between the signal output line and the last-stage signal transmission line for selectively connecting and disconnecting the signal output line to and from the last-stage signal transmission line; and a fourth switch provided between the ground line and a junction between the signal output line and the third switch for selectively connecting and disconnecting the ground line to and from the junction between the signal output line and the third switch.